122 FUNGOID PESTS OF CULTIVATED PLANTS. 



he set to work to prove by cultures that the Pear fungus would produce 

 the Savin fungus by inoculation, and vice versa. (Fig. 1G.) 



Incidentally Stevenson records that the Savin fungus is found in 

 Scotland, but that the other condition, the Pear-leaf fungus, is not a 

 Scottish plant. 



The advice given to gardeners by the theorists is to destroy all Savin 

 bushes, root and branch, if they would save their Pear trees. Berkeley, 

 however, wrote: — "If picking the leaves off carefully and burning them 

 will not do, we may feel secure that an onslaught against the poor Savin 

 bushes will not avail us." 



Known in France, Germany, Switzerland, Austria, and North America. 



Sacc Syll. vii. 2608 ; Cooke M. F. 193, t. 2, f. 2021 ; Ploirr. Brit. Ured. 

 p. 230; Mass. PL Dis. 257; Thilm. Pom. 73 ; Cooke Hdbk. No. 1597 ; 

 Gard. Chroii. 1862, p. 689; Tubeuf, Dis. 399, fig. 



Pear-leap Blister. 

 Exoascus bullatus (Tub), PI. X. fig. 9. 



The blister of Pear leaves is a disease which has long been known in 

 this country, distorting the foliage in a similar manner to the "curl " on 

 Peach leaves. 



The under surface of the leaves is occupied by the external manifesta- 

 tions of the fungus, but the mycelium penetrates the leaf. The glaucous 

 appearance of the hollows of the blisters consists of tufts of small 

 cylindrical cells, or asci, each containing eight small ovate uncoloured 

 sporidia (5 ^ diam.). When these sporidia are mature the asci are ruptured 

 at the apex, and they escape. 



When first discovered this fungus was called Oidium bullatum, until 

 the presence of asci was determined. 



" In many cases these blisters formed two parallel lines on either 

 side of the midrib, but sometimes they were irregularly scattered over 

 the leaf. In some cases the blistered part had become black, and in 

 others the portion of the leaf which had protruded had fallen out, so as to 

 leave a regularly defined aperture. The cavities were found to be lined 

 with a thin white stratum, consisting of myriads of confluent white 

 specks of a waxy rather than a powdery appearance." 



It is incumbent upon the cultivator to pick off all the blistered leaves 

 and burn them, so as to keep a check on reproduction. Spraying young 

 trees with Bordeaux mixture at intervals of a fortnight may be pre- 

 ventive. 



Jowrn. It. U.S. ix. p. 48; Sacc. Syll. viii. 3313; Mass. PI. Dis. 90, 

 fig. 18 ; Cooke Hdbk. No. 2232, fig. 842. 



Pear-leaf Blight. 

 Entomosponum maculatum (Lev.), PI. X. fig. 10. 



This disease is very destructive in the nurseries of the United States, 

 although its presence in this country is rather doubtful. 



Small red spots on the leaves first appear : these increase in size and 

 become brown, or it may extend over the leaf, which then shrivels and 

 falls to the ground. 



